The test cases are designed specifically to se how it handles large and small numbers. The cases 1-3 are the same as 4-6, the later have only minus sign with those 10000 numbers. All the results shall be by design the integer number 31415 (visualised by "10000 x Pi" - as we do not have float format yet). The Pi is simply multiplied or/and divided by large numbers (as we do not have float input yet, it is done by several multiplication/division by 10000). The results are: > test1 31415 ok > test2 31415 ok > test3 |significand| > 16777215
Here the sign is chabged only: > test4 |significand| > 16777215 > test5 31438 ok > test6 |significand| > 16777215 > My current understanding is the division is cousing issues. The lost of significant figures shall not be the case - see the test 1: tmp = pi / (10000^5) pi = tmp * 10000^6 (correct result 31415). The test 2: tmp = pi / 10000 / 10000 pi = tmp * 10000^3 (correct result 31415). Te test 3: tmp = pi / 10000 / 10000 /10000 pi = tmp * 10000^4 (error). The test4-6 are same as the above one, but with minus sign at 10000. So the result shall be 31415 (when ignoring the sign). As you may see from previous test the f/ is sensitive to signs of the operands and gives unpecise results - see for example test5 result. Pito. ----- PŮVODNÍ ZPRÁVA ----- Od: "Leon N Maurer" <leon.mau...@gmail.com> Komu: amforth-devel@lists.sourceforge.net Předmět: Re: [Amforth-devel] Float testing - small/large numbers Datum: 29.8.2010 - 19:17:31 > I don't have my device handy so I can't test your > code. Could you be a little > more clear about which ones failed, what the > results are supposed to be, and > what the results actually are? (When you write > "the result shall be -31415", > is that what it's supposed to be, what it actualy > is, or something else?) > > It looks like you're dividing and then multiplying > by very large powers of 10. > I wouldn't be surprised if you loose some > significant figures by doing this. > -Leon > > ------------------------------------------------------------------------------ > > Sell apps to millions through the Intel(R) > Atom(Tm) Developer Program > Be part of this innovative community and reach > millions of netbook users > worldwide. Take advantage of special opportunities > to increase revenue and > speed time-to-market. Join now, and jumpstart your > future. > http://p.sf.net/sfu/intel-atom-d2d > _______________________________________________ > Amforth-devel mailing list > Amforth-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/amforth-devel ------------------------------------------------------------------------------ Sell apps to millions through the Intel(R) Atom(Tm) Developer Program Be part of this innovative community and reach millions of netbook users worldwide. Take advantage of special opportunities to increase revenue and speed time-to-market. Join now, and jumpstart your future. http://p.sf.net/sfu/intel-atom-d2d _______________________________________________ Amforth-devel mailing list Amforth-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/amforth-devel
